Question

Find an explicit formula for the geometric sequence 3,15,75,375
a(n)=

Answer 1

an = 3(5)^(n-1).

Explanation:

15 / 3 = 5

75/15 = 5

375/75 = 5

So the common ratio is 5.

First term a1 =3

an = a1 r^(n-1) is the explicit formula.

so here we have:

an = 3(5)^(n-1).